Data from: Fire history and plant community composition outweigh decadal multi‐factor global change as drivers of microbial composition in an annual grassland

Soil microbial communities regulate and respond to key biogeochemical
cycles and influence plant community patterns. However, microbial
communities also respond to disturbance events, motivating an assessment
of the relative roles of decadal multi-factor global change, disturbance,
and plant community structure on microbial community responses. We used
high-throughput amplicon sequencing to characterize the diversity and
composition of bacterial and fungal communities in bulk soil (0–7 cm)
collected in 2014 from the Jasper Ridge Global Change Experiment, a
full-factorial field experiment in which ambient and elevated levels of
nitrogen deposition (+7 g N m-2 yr-1 calcium nitrate), CO2 concentration
(+275 ppm), temperature (+1–2 ºC), and precipitation (+50% volume with +3
weeks duration) were applied to a California annual grassland from 1998 to
2014. We used linear mixed-effects modeling to test for the effects of
global change on microbial diversity (observed richness, Shannon index).
We also used generalized dissimilarity modeling (GDM) to study controls on
compositional dissimilarity in fungal and bacterial communities. Bacterial
community composition was best explained by exposure to fires in 2003 and
2011, whereas fungal community composition was best explained by plant
community composition. The richness of fungi increased under elevated
nitrogen deposition; bacterial diversity metrics decreased under warmer
temperatures. Interactions between global change factors were
statistically insignificant or weak. Synthesis. Our results indicate that
even on decadal timescales, the effects of fire history and plant
community composition on bacterial and fungal community composition,
respectively, outweigh the effects of multi-factor global change.
Furthermore, global change factors have mostly additive effects on
microbial diversity patterns. Our results show that highly variable
mediators such as fire history and plant community composition limit the
generalizability of soil microbial responses to long-term global change.